IC chip package with dummy solder structure under corner, and related method

ABSTRACT

An IC chip package includes a substrate having a plurality of interconnect metal pads, and a chip having a plurality of interconnect metal pads arranged thereon. An interconnect solder structure electrically connects each of the plurality of interconnect metal pads. The chip is devoid of the interconnect solder structures and interconnect metal pads at one or more corners of the chip. Rather, a dummy solder structure connects the IC chip to the substrate at each of the one or more corners of the IC chip, and the dummy solder structure is directly under at least one side of the IC chip at the one or more corners of the IC chip. The dummy solder structure has a larger volume than a volume of each of the plurality of interconnect solder structures. The dummy solder structure eliminates a chip-underfill interface at corner(s) of the chip where delamination would occur.

BACKGROUND

The present disclosure relates to integrated circuit (IC) packagefabrication, and more specifically, to a method to improve IC packagereliability by providing dummy solder structures directly under a cornerof the IC chip package instead of a chip corner to underfill (UF)interface.

Integrated circuit (IC) packages provide mechanisms for mounting an ICdie or chip, and scaling wiring connections thereto. A flip chip ballgrid array (FC-BGA) is one type of system used to electrically connectto an IC chip. FC-BGA packages include a plurality of controlledcollapse chip connections (C4), i.e., small interconnect solder bumpconnections, in an array that connect to external circuitry of the ICchip. BGAs provide more interconnections than a flat package or adual-line package because the entire surface of the IC chip is usedrather than just an outer surface of the chip. Most BGAs are assembledon printed circuit boards, carriers or substrates that include atwo-metal layer or multi-layered, high density ceramic substrate ororganic laminate.

FC-BGA packages face the IC chip downwardly to provide a number ofadvantages such as a smaller footprint, easier assembly, reduced signalinductance, higher signal density, and reduced power/ground inductance.In this form, the IC chip has the C4s formed thereon and then is flippedand placed face down so the interconnect solder bumps connect directlyto the substrate. The FC-BGA packages have an UF material, usually anepoxy, or acrylic and silicone material, inserted about the C4s tostabilize the interconnections, seal the interconnections from moistureand provide improved thermal cycling performance. One challenge withFC-BGA IC packages is that they can fail reliability tests due todelamination between the chip and the underfill at a corner of the ICchip. The delamination can lead to the interconnect solder bumps (C4)cracking and electrical failures. Delamination can be caused by cuttingof the IC chips from a wafer. Delamination can also be caused by highstress at a lower temperature side of the IC chip from differentcoefficients of thermal expansion of materials. Delamination can also becaused by reduced adhesion between the underfill and IC chip at thehigher temperature side of the IC chip, e.g., above a glass transitiontemperatures (Tg) of the underfill epoxy, it becomes softer and losesadhesion.

Approaches to address the problem include increasing the adhesionstrength of the chip-underfill interface with grooves or protrusions ordepositing more underfill at the corners of the IC chip. However, eachof these approaches complicates the IC chip and/or package fabrication.Another approach adds dummy interconnect solder bumps near the cornersof the IC chip that are identical to the active interconnect solderbumps. However, since interconnect solder bumps are placed on the ICchip before dicing of the chip from a wafer, such placement can violatedicing rules that prohibit dicing immediately adjacent to interconnectsolder bumps. Notably, dicing in close proximity to interconnect solderbumps can lead to undesired removal of some of the interconnect solderbumps. Another approach increases the glass transition temperature (Tg)of the underfill, but this can lead to fillet cracking and may limitunderfill material selection. Reduction in lid thickness and/or lidfootprint to reduce stress has also been attempted, but these approachescan degrade package co-planarity and can impact yield.

SUMMARY

A first aspect of the disclosure is directed to an integrated circuit(IC) chip package, comprising: a substrate having a first plurality ofinterconnect metal pads thereon; an integrated circuit (IC) chip havinga second plurality of interconnect metal pads arranged thereon; aninterconnect solder structure electrically connecting each of the firstand second plurality of interconnect metal pads, the IC chip beingdevoid of the interconnect solder structures at one or more corners ofthe IC chip; and a dummy solder structure connecting the IC chip to thesubstrate at each of the one or more corners of the IC chip, and whereinthe dummy solder structure is directly under at least one side of the ICchip at the one or more corners of the IC chip, and wherein the dummysolder structure has a larger volume than a volume of each of theplurality of interconnect solder structures.

A second aspect of the disclosure includes a method, comprising: forminga first plurality of interconnect metal pads on an integrated circuit(IC) chip, except at one or more corners of the IC chip, and forming afirst mounting metal pad in the one or more corners of the IC chip;forming a plurality of interconnect solder structure on the firstplurality of interconnect metal pads on the IC chip; forming on asubstrate: a second plurality of interconnect metal pads configured tocouple with the first plurality of interconnect metal pads on the ICchip using the plurality of interconnect solder structures, and a secondmounting metal pad at one or more locations of the substrate that areconfigured to align with a respective first mounting metal pad, eachsecond mounting metal pad having a larger area than each of the firstand second plurality of interconnect metal pads; forming a dummy solderstructure on each second mounting metal pad on the substrate, each dummysolder structure being larger in area than each interconnect solderstructure; and mounting the IC chip to the substrate, resulting in theplurality of interconnect solder structures interconnecting the firstand second plurality of interconnect metal pads and the dummy solderstructure interconnecting the one or more corners of the IC chip to thesubstrate.

A third aspect is directed to an integrated circuit chip, comprising: abody having circuitry therein; a plurality of interconnect metal pads ona surface of the body, the plurality of interconnect metal padsconnected to the circuitry and each configured to receive aninterconnect solder structure for electrically connecting the pluralityof interconnect metal pads to a substrate; and a mounting metal pad inone or more corners of the body, the mounting metal pad having a largerarea than the plurality of interconnect metal pads, the mounting metalpad configured to connect a dummy solder structure that is larger involume than the interconnect solder structure to the body.

The foregoing and other features of the disclosure will be apparent fromthe following more particular description of embodiments of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of this disclosure will be described in detail, withreference to the following figures, wherein like designations denotelike elements, and wherein:

FIG. 1 shows a side view of an integrated circuit (IC) chip havinginterconnect and mounting metal pads formed thereon, according toembodiments of the disclosure.

FIG. 2 shows a plan view of the IC chip having interconnect and mountingmetal pads thereon, according to embodiments of the disclosure.

FIG. 3 shows a side view of the IC chip having interconnect solderstructures formed thereon, according to embodiments of the disclosure.

FIG. 4 shows a plan view of the IC chip having interconnect solderstructures thereon, according to embodiments of the disclosure.

FIG. 5 shows a side view of an integrated circuit (IC) chip havingmounting metal pads formed thereon, according to another embodiment ofthe disclosure.

FIG. 6 shows a plan view of the IC chip having mounting metal padsthereon, according to another embodiment of the disclosure.

FIG. 7 shows a side view of the IC chip having interconnect metal padsand interconnect solder structures formed thereon, according to anotherembodiment of the disclosure.

FIG. 8 shows a plan view of IC chips on a wafer having mounting metalpads thereon, according to yet another embodiment of the disclosure.

FIG. 9 shows a plan view of IC chips on a wafer having mounting metalpads thereon, according to other embodiments of the disclosure.

FIG. 10 shows a plan view of IC chips on a wafer having mounting metalpads thereon, according to additional embodiments of the disclosure.

FIG. 11 shows a side view of a substrate having interconnect metal pads,mounting metal pads and dummy solder structures formed thereon,according to an embodiment of the disclosure.

FIG. 12 shows a side view of mounting an IC chip to a substrate,according to embodiments of the disclosure.

FIG. 13 shows a side view of the IC chip mounted to the substrate,according to embodiments of the disclosure.

FIG. 14 shows a side view of injecting underfill between the IC chip andthe substrate, and an IC package, according to embodiments of thedisclosure.

FIG. 15 shows a plan view of the IC package through view line 15-15 ofFIG. 14.

FIG. 16 shows a side view of an IC package, according to otherembodiments of the disclosure.

It is noted that the drawings of the disclosure are not necessarily toscale. The drawings are intended to depict only typical aspects of thedisclosure, and therefore should not be considered as limiting the scopeof the disclosure. In the drawings, like numbering represents likeelements between the drawings.

DETAILED DESCRIPTION

Embodiments of the disclosure provide an integrated circuit (IC) packageand related method that use a dummy solder structure connecting the ICchip to the substrate at one or more corners of the IC chip. The dummysolder structure prevents underfill from forming under the corners ofthe IC chip where employed, and thus prevents chip-underfilldelamination at the corners where delamination is usually initiated.Since the dummy solder structures are metal pads during dicing andreceive solder from the laminate, their placement at the corner(s) ofthe IC chip does not violate dicing rules.

Referring to FIGS. 1-16, methods and IC packages according to variousembodiments of the disclosure will be described.

FIGS. 1-11 show forming metal pads and interconnect solder structures onan integrated circuit (IC) chip or die 110 (hereinafter “IC chip 110”).IC chip 110 may include a body 111 having any now known or laterdeveloped IC chip circuitry therein, e.g., digital, analog, mixed,logic, comparator, switches, audio amplifiers, operational amplifiers,timers, etc. FIG. 1 shows a side view of a wafer 108 including a numberof IC chips 110, e.g., two. While two IC chips 110 are shown, it isappreciated that a much larger number of IC chips 110 may be formed ineach wafer; see e.g., FIGS. 8-10. Metal pads and interconnect solderstructures may be formed on IC chip in a number of ways.

In one embodiment, shown in FIGS. 1-4, all of the metal pads may beformed using the same mask. FIG. 1 shows forming a first plurality ofinterconnect metal pads 112 and first mounting metal pad 114 on IC chip110, i.e., on a surface 116 of IC chip 110. Interconnect metal pads 112are formed except at one or more corners 120 of IC chip 110, wheremounting metal pad(s) 114 are formed. FIG. 2 shows a plan view of asingle IC chip 110 with first plurality of interconnect metal pads 112and first mounting metal pad(s) 114 thereon. A dashed box in FIG. 2 (andFIGS. 4, 6 and 15) shows the outline of circuitry within IC chip 110. Asused herein, “interconnect metal pads” are electrically connected tointernal wiring within body 111 of IC chip 110 that extends to surface116 of IC chip 110, and are used for active, electrical interconnectionto wiring of a substrate, as described herein. In contrast, “mountingmetal pad(s)” are not electrically connected to internal wiring of ICchip 110, are electrically inactive and act to physically connect ICchip 110 to a substrate, as described herein.

In FIG. 1 forming first plurality of interconnect metal pads 112 andfirst mounting metal pad(s) 114 includes forming a mask 122 over a seedlayer 124 on IC chip 110, i.e., on surface 116. Seed layer 124 mayinclude any appropriate material that allows formation of interconnectmetal pads 112 on surface 116. “Mask” as used herein may refer to alayer of material which is applied over an underlying layer of material,and patterned to have openings, so that the underlying layer can beprocessed where there are openings. After processing the underlyinglayer, the mask may be removed. Common masking materials are photoresist(resist) and nitride. Nitride is usually considered to be a “hard mask.”As illustrated, mask 122 includes a first set of openings 130B exposingareas for interconnect metal pads 112 and a second set of largeropenings 130A exposing areas for mounting metal pads 114. Asillustrated, openings 130A for mounting metal pads 114 are at leastlaterally larger than openings 130B for interconnect metal pads 112.Openings 130A may extend into a dicing channel 134 through which adicing tool, e.g., a laser, will cut IC chip 110 from wafer 108.Openings 130A may extend slightly over circuitry within IC chip 110, buttypically this would be to a minimal extent. Openings 130 are providedin one or more corners 120 of IC chip 110 at which chip-underfilldelamination or other stress-related issues are to be addressed. Asunderstood, dicing channels 134 are laterally outside of circuitrywithin IC chip 110; thus dicing through channels 134 does not damagecircuitry within IC chip 110.

Interconnect metal pads 112 and mounting metal pads 114 may be formed infirst set of openings 130B and second set of larger openings 130A inmask 122 by depositing material, e.g., a conductor, and planarizing toremove any excess material. “Depositing” may include any now known orlater developed techniques appropriate for the material to be depositedincluding but are not limited to, for example: chemical vapor deposition(CVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD),semi-atmosphere CVD (SACVD) and high density plasma CVD (HDPCVD), rapidthermal CVD (RTCVD), ultra-high vacuum CVD (UHVCVD), limited reactionprocessing CVD (LRPCVD), metalorganic CVD (MOCVD), sputteringdeposition, ion beam deposition, electron beam deposition, laserassisted deposition, thermal oxidation, thermal nitridation, spin-onmethods, physical vapor deposition (PVD), atomic layer deposition (ALD),chemical oxidation, molecular beam epitaxy (MBE), plating, evaporation.In one non-limiting example, interconnect metal pads 112 and mountingmetal pads 114 may include nickel-gold alloy formed by ALD. After metalpad formation, mask 122 may be removed using any now known or laterdeveloped ashing process.

FIG. 3 shows a side view of forming a plurality of interconnect solderstructures 140. FIG. 3 shows forming a mask 142 over surface 116 of ICchip 110. Mask 142 may include any of the materials of mask 122. Mask142 covers mounting metal pad(s) 114, e.g., at corner(s) 120 of IC chip110, and includes a third set of openings 144 exposing interconnectmetal pads 112. Interconnect solder structures 140 are formed in thirdset of openings 144, e.g., by deposition of the desired material andplanarization to remove excess material. In one non-limiting example,interconnect solder structures 140 may include tin-silver bumps orcopper pillars. As used herein, “interconnect solder structures” areelectrically connected to interconnect metal pads 112 on surface 116 ofIC chip 110, and are used for active, electrical interconnection towiring of a substrate, as described herein. Although shown as balls,interconnect solder structures 140 may include any now known or laterdeveloped ball grid array or C4 type conductive structure including butnot limited to balls, bumps and/or pillars. As shown in the plan view ofFIG. 4 of a single IC chip 110, mask 142 may be removed using any nowknown or later developed ashing process.

FIGS. 5-10 show another embodiment for forming interconnect metal pads112 and mounting metal pad(s) 114 on IC chip 110, using more than onemask for the metal pads. FIG. 5 shows a side view and FIG. 6 shows aplan view of forming mounting metal pads 114, according to thisembodiment. In this embodiment, as shown in FIG. 5, a mask 150 is formedover seed layer 124 on IC chip 110, i.e., surface 116 thereof. Mask 150may be substantially similar to mask 122, described previously. Mask 150may include a set of openings 152 exposing areas for mounting metal pads114 only. Openings 152 may extend into dicing channel 134 between ICchips 110 on wafer 108—see center of FIG. 5. Openings 152 may extendslightly over circuitry within IC chip 110, but typically this would beto a minimal extent. FIG. 5 also shows forming mounting metal pads 114in set of openings 152 using mask 150. In one non-limiting example,mounting metal pads 114 may include nickel-gold alloy formed by ALD. Anyexcess material may be removed by planarization. Mask 150 may be removedusing any now known or later developed ashing process.

FIG. 7 shows a side view of forming interconnect solder structures 140and interconnect metal pads 112 with a single mask. In this embodiment,a mask 156 is formed on IC chip 110, i.e., on surface 116. Mask 156covers mounting metal pads 114 and includes a set of openings 158exposing areas for interconnect metal pads 112 and interconnect solderstructures 140. Each of openings 158 is smaller than each of openings152 (FIG. 5) in mask 150 (FIG. 5) used to form mounting metal pads 114.FIG. 5 also shows forming interconnect metal pads 112 and interconnectsolder structures 140 in set of openings 158. Interconnect metal pads112 and interconnect solder structures 140 may be formed in openings bysequentially depositing the desired material, e.g., conductors. In onenon-limiting example, interconnect metal pads 112 may includenickel-gold alloy formed by ALD, and interconnect solder structures 140may include tin-silver bumps or copper pillars formed by ALD. As noted,although shown as balls, interconnect solder structures 140 may includeany now known or later developed ball grid array or C4 type conductivestructure including but not limited to balls, bumps and/or pillars. Mask156 may be removed using any now known or later developed ashingprocess. The finished structure is the same as shown in the plan view ofFIG. 4.

While a number of processes have been described for forming interconnectmetal pads 112, mounting metal pads 114 and interconnect solderstructures 140, it is recognized that a large variety of otherapproaches are possible, and are considered within the skill in the art.In one other non-limiting example, a custom tool may be created thatallows formation of all of the structures with a single mask.

FIGS. 8-10 show enlarged plan views of corners 120 of a number of ICchips 110 on wafer 108, and including mounting metal pads 114 extendinginto dicing channel 134. As illustrated, although shown as L-shaped incross-sectional in FIGS. 2, 4 and 6, mounting metal pads 114 can take avariety of shapes, and can extend laterally outward of circuitry withinIC chip 110 (shown by dashed lines adjacent dicing channels 134).Similarly, a shape of a dummy solder structure 182 (FIGS. 13-16), aswill be described, formed on mounting metal pads 114 may have a varietyof shapes. The shape of mounting metal pads 114 (and dummy solderstructures 182) can be user defined, and can vary depending on manyfactors including but not limited to the shape and/or dimensions ofcircuitry within IC chip 110, the desired outside shape and/ordimensions of IC chip 110 (i.e., beyond the circuitry), and/or the shapeand/or dimensions of substrate 166, the type of underfill 190 used,and/or the expected chip-underfill delamination or other stress-relatedissues. In any event, IC chip 110 does not include any interconnectsolder structures 140 in corner(s) 120. Accordingly, when diced fromwafer 108, IC chip 110 does not lose any interconnect solder structures140.

FIG. 11 shows a side view of a substrate 166 according to embodiments ofthe disclosure. As used herein, “substrate” may include any structureupon which IC chip 110 may be mounted for electrical connection scalingand IC package formation. Substrate 166 may include, for example, aprinted circuit board, carrier, or laminate, each of which includes atwo-metal layer or multi-layered, high density ceramic or organicmaterials. Substrate 166 includes wiring therein to scale frominterconnect metal pads 170 thereof.

FIG. 11 also shows interconnect metal pads 170 on substrate 166.Interconnect metal pads 170 on substrate 166 are configured to couplewith interconnect solder structures 140 on IC chip 110. Interconnectmetal pads 170 on substrate 166 may be provided as part of substrate166, or may be formed thereon using any now known or later developedmasked solder paste or place-solder structure process. In thenon-limiting example shown, interconnect metal pads 170 on substrate 166may be formed using a mask 174 having a set of openings 176 therein.Openings 176 expose a seed layer 178 on substrate 166, i.e., on surfacethereof. Seed layer 178 may include any appropriate material that allowsformation of interconnect metal pads 170. Interconnect metal pads 170may be formed in openings 176 by depositing, for example, copper by,e.g., by ALD. Interconnect metal pads 170 may be solderless (as shown),or they may include solder thereon, e.g., tin (Sn), nickel-gold alloy(Ni/Au), nickel-palladium-gold alloy (Ni/Pd/Au) or other solders. FIG.11 also shows mounting metal pad(s) 180 at one or more locations ofsubstrate 166. Mounting metal pad(s) 180 may be provided on substrate166, or formed thereon with interconnect metal pads 170 or in a separatemasking process. Mounting metal pad(s) 180 are configured to align witha respective mounting metal pad 114 (FIG. 7) on IC chip 110. To matchmounting metal pad 114 on IC chip 110, each mounting metal pad 180 onsubstrate 166 has a larger area than each of first and second pluralityof interconnect metal pads 112 (FIG. 7) and 170, and is typicallycommensurate in area (and perhaps shape) with mounting metal pad(s) 114on IC chip 110. Thus, forming mounting metal pads 114, 180 includesforming them both with larger area than each of interconnect metal pads112, 170. Mounting metal pad(s) 180 does not have to be the same size orshape as mounting metal pad(s) 114 on IC chip 110, but it can be thesame size and/or shape. In certain embodiments, metal mounting pad(s)180 may be formed on substrate 166 such that they extend laterallybeyond at least one side 188 of IC chip 110 after mounting the IC chipto the substrate (see e.g., FIG. 16).

FIG. 11 also shows forming a dummy solder structure 182 on each mountingmetal pad 180 on substrate 166. Dummy solder structure 182 may be formedin a set of openings 184 in mask 174, e.g., by deposition of the desiredmaterial as part of second masked solder paste or place-solder structureprocess. Alternatively, as with interconnect solder structures 140 on ICchip 110, one mask may be used to form interconnect metal pads 170, andanother mask used to form mounting metal pads 180 and dummy solderstructures 182. As used herein, “dummy solder structures,” as will bedescribed, physically connect mounting metal pads 114 on surface 116 ofIC chip 110 and mounting metal pads 180 on substrate 166, but areelectrically inactive. Although shown as blocks, interconnect metal pads170 may include any now known or later developed metal pads. In onenon-limiting example, dummy solder structures 182 may include tin-silverbumps or copper pillars. As illustrated, in certain embodiments, dummysolder structures 182 have a larger volume than a volume of each of theplurality of interconnect solder structures 140, i.e., individually. Thelarger volume allows for wider distribution of dummy solder structures182 within corner(s) 120, which as will be described, allows for greaterseparation of underfill 190 (FIG. 14-16) from corner(s) 120 and thus alarger reduction in stress. In certain embodiments, dummy solderstructure 182 may also include a solder material that is softer than thesolder material of each of interconnect solder structures 140. Thesofter solder material may allow for more stress reduction at thechip-underfill interface. The softer solder material may also allow morecoining (compaction and/or distribution) of dummy solder structure 182compared to interconnect solder structures 140 to allow for desiredspacing of IC chip 110 and substrate 166 despite dummy solder structures182 being of larger volume. Each dummy solder structure 182 may belarger in area than each interconnect solder structure 140.

FIG. 12 shows a side view of mounting IC chip 110 to substrate 166, andFIG. 13 shows a side view of one embodiment of an IC package 200 soformed. At this stage, as shown in FIG. 12, IC chip 110 has been dicedfrom wafer 108. In contrast to conventional IC chips, IC chip 110includes mounting metal pad(s) 114 in corner(s) 120 thereof. Since nointerconnect solder structures 140 were formed in corner(s) 120, IC chip110 does not include any interconnect solder structures in corner(s)120, and it is incapable of losing any during dicing. In certainembodiments, as shown in the left side of FIG. 12, since mounting metalpads 114 are formed in each of corner(s) 120 of IC chip 110 prior todicing the IC chip from wafer 108, and they may be formed in dicingchannels 134 (FIGS. 1, 3, 5, 7-10), when IC chips 110 are diced, anouter side 186 of mounting metal pads 180 may be coplanar with side 188of IC chip 110. That is, mounting metal pad 114 extends through side 188of IC chip 110 after dicing the IC chip from wafer 108. That is, thedicing tool will pass through a center portion of dicing channel 134,which leaves a portion of mounting metal pad 114 on corner(s) 120 of thediced IC chip beyond the circuitry therein. In this case, the dicingtool cuts mounting metal pads 114 and IC chip 110 to have coplanar sides186, 188. A portion of mounting metal pads 114 may extend slightly overcircuitry within IC chip 110 (see, e.g., FIGS. 9 and 15), but typicallythis would be to a minimal extent. In other embodiments, depending onthe spacing between adjacent IC chips' 110 mounting metal pads 114, asshown in right side of FIG. 12, some extent of dicing channel 134 mayremain to separate outer side 186 of mounting metal pads 114 from side188 of IC chip 110.

IC chip 110 may be mounted to substrate 166 using any now known or laterdeveloped process, e.g., aligning, positioning together and thermalreflow. The mounting results in interconnect solder structures 140 (fromIC chip 110) connecting interconnect metal pads 112 and 170, and dummysolder structure 182 connecting one or more corners 120 of IC chip 110to substrate 166, e.g., using mounting metal pads 114, 180.

FIG. 14 shows forming an underfill 190 extending between IC chip 110 andsubstrate 166 and into an area about interconnect solder structures 140and dummy solder structure 182. As illustrated, however, dummy solderstructure 180 prevents the underfill 190 from being under one or morecorners 120 of IC chip 110. FIG. 15 shows a plan view along view line15-15 in FIG. 14 illustrating how dummy solder structure 180 preventsunderfill 190 from being present in corner(s) 120 of IC chip 110. Incertain embodiments, as shown in FIG. 16, dummy solder structure 182 atcorner(s) 120 of IC chip 110 may extend laterally outward beyond atleast one side 188 of IC chip 110.

FIGS. 13, 14 and 16 show side views of an IC package 200 according tovarious embodiments of the disclosure. IC package 200 includes substrate166 having a first plurality of interconnect metal pads 170 thereon. ICchip package 200 also includes IC chip 110 having a second plurality ofinterconnect metal pads 112 arranged thereon, and an interconnect solderstructure 140 electrically connecting each of first and second pluralityof interconnect metal pads 112, 170. IC chip 110 is devoid ofinterconnect solder structures 140 at one or more corners 130 of the ICchip. Rather, IC chip package 120 includes dummy solder structure 182connecting IC chip 110 to substrate 166 at each of the one or morecorners 120 of the IC chip. IC chip package 200 may include mountingmetal pad(s) 114 in corner(s) 120 of IC chip 110 that are configured tocouple to dummy solder structure 182, and mounting metal pad(s) 180 onsubstrate 166 that are configured to couple to dummy solder structure182. Metal pads 112, 114, 170, 180 may be made of, for example, anickel-gold alloy.

Dummy solder structure 182 thus mechanically couples respective mountingmetal pads 114, 180 together. Hence, dummy solder structure 182 andrespective mounting metal pads 114, 180 are electrically inactive, incontrast to interconnect solder structures 140 and respectiveinterconnect metal pads 112, 170 that are electrically active, i.e.,they carry electrical current. In contrast to conventional interconnectsolder structures, dummy solder structure 182 is directly under side(s)188 of each of corner(s) 120 of IC chip 110, where employed. That is, atleast part of dummy solder structure 182 is aligned vertically underside(s) 188 of IC chip 110. An underfill 190 may extend between IC chip110 and substrate 166 and into an area about the interconnect solderstructures 140 and dummy solder structure 182. However, in contrast toconventional IC packages, dummy solder structure 182 prevents underfill190 from being under a respective corner(s) 120 of the IC chip, whicheliminates the chip-underfill interface at the corner(s) and the relateddelamination and stress-related issues.

Dummy solder structure 182 may also have a larger volume than a volumeof each of interconnect solder structures 140. Mounting metal pads 114,180 may also be larger in area than each of interconnect metal pads 112,170 to accommodate the larger volume of dummy solder structure 182. Thelarger solder volume and metal pad size can be customized to create anydesired sized dummy solder structure 182. For example, in certainembodiments, dummy solder structure 182 is directly under side(s) 188 ofeach of corner(s) 120 of IC chip 110, but does not extend laterallybeyond side(s) 188. In this case, mounting metal pad 180 on substrate166 may be aligned with or nearly aligned with side 188 of IC chip 110.In other examples, shown in the left side of FIG. 13 and FIG. 16, dummysolder structure 182 may extend laterally outward beyond side(s) 188 ofIC chip 110. That is, dummy solder structure 182 extends under andbeyond side(s) 188 of IC chip 110, outside the boundary of the chip. Inthis latter case, as shown in FIG. 16, mounting metal pad 180 onsubstrate 166 may also extend laterally beyond side 188 of IC chip 110.

As noted, each dummy solder structure 182 and each interconnect solderstructure 140 may include, for example, one of a tin-silver alloy andcopper. In certain embodiments, however, dummy solder structure 182 mayinclude a solder material that is softer than a different (in at leasthardness), second solder material of interconnect solder structures 140to reduce the stress at the chip-underfill interface. Because mountingmetal pad 180 in corner(s) 120 of IC chip 120 is/are in a dicing channel134 of the IC chip, in contrast to conventional IC chips, mounting metalpad 180 may extend through a side 188 of IC chip 110 after the chip isdiced from wafer 108.

While example materials have been listed herein for metal pads andsolder structures, it is recognized that any now known or laterdeveloped materials used for such structures that otherwise meet thelimitations described herein may be employed.

While dummy solder structures 182 and mounting metal pads 114, 180 havebeen illustrated in each corner 120 of IC chip package 200, they may beselectively used in only corners 120 where chip-underfill delaminationor other stress-related issues are a concern.

Embodiments of the disclosure provide embodiments of IC package 200, ICchip 100 and related methods that use dummy solder structure 182connecting IC chip 110 to substrate 166 at one or more corners 120 ofthe IC chip. Dummy solder structure 182 prevents underfill 190 fromforming under the corner(s) 120 of IC chip 110, and thus preventschip-underfill delamination at the corners where delamination isnormally prevalent. Since dummy solder structures 182 are inactive,their placement at corner(s) 120 of the IC chip does not violate dicingrules. Dummy solder structures 182 may also be larger than the activeinterconnect solder structures, i.e., controlled collapse chipconnections (C4), and thus are more immune to damage caused by dicing.While embodiments of the disclosure have been described relative toFC-BGA applications, it is emphasized that the teachings are equallyapplicable to land grid arrays (LGA) or other package-to-cardinterconnect options.

The method as described above is used in the fabrication of integratedcircuit chips and chip packages. The resulting integrated circuit chipscan be distributed by the fabricator in raw wafer form (that is, as asingle wafer that has multiple unpackaged chips), as a bare die, or in apackaged form. In the latter case, the chip is mounted in a single chippackage (such as a plastic carrier, with leads that are affixed to amotherboard or other higher level carrier) or in a multichip package(such as a ceramic carrier that has either or both surfaceinterconnections or buried interconnections). In any case, the chip isthen integrated with other chips, discrete circuit elements, and/orother signal processing devices as part of either (a) an intermediateproduct, such as a motherboard, or (b) an end product. The end productcan be any product that includes integrated circuit chips, ranging fromtoys and other low-end applications to advanced computer products havinga display, a keyboard or other input device, and a central processor.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. “Optional” or “optionally” means thatthe subsequently described event or circumstance may or may not occur,and that the description includes instances where the event occurs andinstances where it does not.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” “approximately,” and “substantially,” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged, such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.“Approximately” as applied to a particular value of a range applies toboth values, and unless otherwise dependent on the precision of theinstrument measuring the value, may indicate +/−10% of the statedvalue(s).

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present disclosure has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the disclosure in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the disclosure. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A method, comprising: forming a first pluralityof interconnect metal pads on an integrated circuit (IC) chip, except atone or more corners of the IC chip, and forming a first mounting metalpad in the one or more corners of the IC chip; forming a plurality ofinterconnect solder structures on the first plurality of interconnectmetal pads on the IC chip, wherein the IC chip is devoid of theinterconnect solder structures at the one or more corners of the ICchip; forming on a substrate: a second plurality of interconnect metalpads configured to couple with the first plurality of interconnect metalpads on the IC chip using the plurality of interconnect solderstructures, and a second mounting metal pad at one or more locations ofthe substrate that are configured to align with a respective one of thefirst mounting metal pads, each of the second mounting metal pads havinga larger area than each of the first and second plurality ofinterconnect metal pads; forming a dummy solder structure on each of thesecond mounting metal pads on the substrate, each of the dummy solderstructures being larger in area than each of the interconnect solderstructures; mounting the IC chip to the substrate, resulting in theplurality of interconnect solder structures interconnecting the firstand second plurality of interconnect metal pads and the dummy solderstructure interconnecting the one or more corners of the IC chip to thesubstrate; and forming an underfill extending between the IC chip andthe substrate and into an area surrounding the interconnect solderstructures and the dummy solder structure, wherein the dummy solderstructure prevents the underfill from being disposed under a respectiveone of the corners of the IC chip.
 2. The method of claim 1, whereinforming the first plurality of interconnect metal pads and the firstmounting metal pad on the IC chip includes: forming a first mask over aseed layer on the IC chip, the first mask including a first set ofopenings exposing areas for the first plurality of interconnect metalpads and a second set of larger openings exposing areas for the firstmounting metal pads, forming the first plurality of interconnect metalpads and the first mounting metal pads in the first set of openings andthe second set of larger openings, and removing the first mask; andwherein forming the plurality of interconnect solder structuresincludes: forming a second mask over a surface of the IC chip, thesecond mask covering the first mounting metal pads and including a thirdset of openings exposing the first plurality of interconnect metal pads,forming the plurality of interconnect solder structures in the third setof openings, and removing the second mask.
 3. The method of claim 1,wherein forming the first plurality of interconnect metal pads and thefirst mounting metal pad on the IC chip includes: forming a first maskover a seed layer on the IC chip, the first mask including a first setof openings exposing areas for the first mounting metal pads, formingthe first mounting metal pads in the first set of openings using thefirst mask, and removing the first mask; and wherein forming theplurality of interconnect solder structures includes: forming a secondmask on the IC chip, the second mask covering the first mounting metalpads and including a second set of openings exposing areas for the firstplurality of interconnect metal pads and the plurality of interconnectsolder structures, wherein each of the second set of openings is smallerthan each of the first set of openings in the first mask, forming thefirst plurality of interconnect metal pads and the plurality ofinterconnect solder structures in the second set of openings, andremoving the second mask.
 4. The method of claim 1, wherein forming thefirst mounting metal pad in each of the one or more corners of the ICchip occurs prior to dicing the IC chip from a wafer, and also includesforming the first mounting metal pad in a dicing channel on the wafer,and wherein the first mounting metal pad extends through a side of theIC chip after dicing the IC chip from the wafer.
 5. The method of claim1, wherein forming the first and second mounting metal pads includesforming the first and second mounting metal pads with larger area thaneach of the first and second plurality of interconnect metal pads. 6.The method of claim 1, wherein the dummy solder structure includes afirst solder material that is softer than a different, second soldermaterial of each of the plurality of interconnect solder structures. 7.The method of claim 1, wherein the dummy solder structure at the one ormore corners of the IC chip extends laterally outward beyond at leastone side of the IC chip.
 8. The method of claim 1, wherein the dummysolder structure has a larger volume than a volume of each of theplurality of interconnect solder structures.
 9. An integrated circuit(IC) chip package, comprising: a substrate having a first plurality ofinterconnect metal pads and a first plurality of mounting metal padsarranged thereon, the first plurality of interconnect metal padselectrically connected to internal wiring of the substrate, and thefirst plurality of mounting metal pads not electrically connected to theinternal wiring of the substrate; an integrated circuit (IC) chip havinga second plurality of interconnect metal pads and a second plurality ofmounting metal pads arranged thereon, the second plurality ofinterconnect metal pads electrically connected to internal wiring of theIC chip, and the second plurality of mounting metal pads notelectrically connected to the internal wiring of the IC chip; aninterconnect solder structure connecting each of the first and secondplurality of interconnect metal pads, the IC chip being devoid of theinterconnect solder structures at one or more corners of the IC chip; adummy solder structure connecting the first and second plurality ofmounting metal pads; and an underfill extending between the IC chip andthe substrate and into an area surrounding the interconnect solderstructures and the dummy solder structure, wherein the dummy solderstructure prevents the underfill from being disposed under a respectiveone of the corners of the IC chip.
 10. The IC chip package of claim 9,wherein the dummy solder structure is directly under at least one sideof the IC chip at the one or more corners of the IC chip, and wherein atleast one dummy solder structure extends laterally outward beyond the atleast one side of the IC chip.
 11. The IC chip package of claim 9,wherein the dummy solder structure includes a first solder material thatis softer than a different, second solder material of the interconnectsolder structures.
 12. The IC chip package of claim 9, wherein eachdummy solder structure and each interconnect solder structure includesone of a tin-silver alloy and copper.
 13. The IC chip package of claim9, wherein the dummy solder structure has a larger volume than a volumeof each of the interconnect solder structures.
 14. The IC chip packageof claim 9, further comprising: a first mounting metal pad in the one ormore corners of the IC chip, the first mounting metal pad configured tocouple to the dummy solder structure; and a second mounting metal pad onthe substrate, the second mounting metal pad configured to couple to thedummy solder structure, wherein the dummy solder structure mechanicallycouples respective first and second mounting metal pads together, andwherein each of the first and second mounting metal pads are larger inarea than each of the first and second plurality of interconnect metalpads.
 15. The IC chip package of claim 14, wherein the dummy solderstructure is directly under at least one side of the IC chip at the oneor more corners of the IC chip, and wherein the second mounting metalpad on the substrate extends laterally beyond the at least one side ofthe IC chip.
 16. The IC chip package of claim 14, wherein the dummysolder structure and respective first and second mounting metal pads areelectrically inactive, and each interconnect solder structure andrespective interconnect metal pad are electrically active.
 17. The ICchip package of claim 14, wherein the first mounting metal pad in theone or more corners of the IC chip is in an area adjacent a dicingchannel of the IC chip.
 18. The IC chip package of claim 14, wherein thefirst mounting metal pad extends through a side of the IC chip.